I'm having the same issues as you... '97 V6.

Looking forward to what you find. I need to replace my cats, O2 sensors, and clean/rebuild the fuel injectors. Hopefully that will fix my problem.

 

I put the fuel pressure gauge in, and I'm getting 47 PSI. This seems to indicate that it's the FPR that needs to be replaced, correct? I assume it should be a constant 4 bar (i.e., 58 PSI)?

I've also noticed that the engine is slow to respond when I take my foot off the gas (i.e., it takes a second for the needle to drop back to idle, and seems to do so very slowly). Does this mean I need a new throttle body as well? I had opened it up and noticed some grease had gotten onto the contacts (the ones that rotate back and forth). I tried my best to clean this, but maybe this wasn't enough?

Could it be that I need to replace both the TB and FPR?

I also noticed that when the A/C is off, the idle is at 1200, whereas when the A/C is on, the A/C is around 800 (i.e., normal). Of course, this is with the CEL on (the original problem is that with the CEL off, the idle is all over the place, sometimes to the point of stalling when the engine is cold).

 

My car 1.8t is also doing the same sort of thing but not extremely rough idle. The only code I got was P0301 (cylinder no 1 misfire detected). What are the cost of the FPR and the throttle body and regulator? Could cheap gas cause this problem?

 

What is the CEL?

 

Where did you buy your MAF from?

If it's not a genuine Audi/VW new or rebuilt, swap it with a new one from the dealer. I can't tell you how many times I've chased my tail over rough idles or misfires and it's turned out to be a faulty MAF that was just replaced with a crappy aftermarket rebuild.

 

I got the aftermarket one from ECS Tuning. The readings from VCDS show that it's within acceptable limits, that's why I figured it was fine. I may try swapping it though.

I'm beginning to think that it's the throttle body, since the needle is slow to drop when it's partially open. Plus the computer seems to have a hard time maintaining a constant speed once I turn the a/c off (the idle speed will start to slowly increase). I just ordered a replacement, we'll see if that works.

 

Check engine light

 

If it's just one cylinder, you likely just need a new ignition coil. Number 1 is closest to the radiator.

 

What's your KG/S at idle, warm engine with A/C off? Does it change with the A/C on?

 

I went by a stealership and bought the OEM MAF. That in combination with a new TB seems to have solved the problem.

I'm pretty pissed off that most of this problem seems to have been caused by ECS selling me a faulty part.